Elephant Cage

It doesn’t exist anymore (and was relatively short-lived,) and contrary to its nickname, it didn’t house pachyderms. It was actually an antenna array, constructed near Wahiawa, Oʻahu, and used during the Cold War.

More formally known as the AN/FRD-10 Circularly Disposed Antenna Array (CDAA) at NCTAMS (Facility 314,) it was a part of the efforts to gather foreign intelligence information.

Along with fourteen other FRD-10 CDAAs worldwide, it was a part of the Naval Security Group’s Classic Bullseye network, a program for strategic signals intelligence (SIGINT) collection and transmitter locating.

This technology was a radical improvement in the performance of high-frequency direction finding. Its design, with uniformly spaced outside the rings of reflector screens, was able to intercept and detect the direction of high-frequency radio transmissions covering 360 degrees. (NPS)

Early work on CDAA systems had been undertaken by the German navy’s signal intelligence research and development center early in World War II. At that time, it was given the name, Wullenweber, or Wullenweber Antenna (named after Jürgen Wullenweber who was the mayor of Lubeck, Germany from 1533 to 1537. He was an opponent of injustice and a supporter of the Protestant cause who became a legendary figure.)

In addition to the nickname noted above, it was referenced by some as a “Dinosaur Cage;“ the names came from the nature of its construction.

The structure had concentric circles of posts and wires; the innermost ring was an antenna reflector screen made up of 80-vertical wood poles 94-feet high that were spaced evenly about 28′-6″ apart in a circle about 732-feet in diameter.

Moving outward, another circle of 40-poles, 58-feet high, spaced evenly a little over 61-feet apart formed a ring 776-feet in diameter. A third ring, 847-feet in diameter consisted of 120 wood poles, 25-feet in height, spaced 22-feet apart. The outer-most ring had 120-poles, 22-feet in height forming a circle with an 873-foot diameter.

With poles, wire and netting, it looked like a cage to control some big animals, thus its nicknames.

But it served a greater purpose; throughout the post-World War II years, advancing technology helped to shift the means of intelligence gathering by the US, from networks of agents operating on the ground in foreign lands to electronic and over flying systems that could gather data from much greater distances.

Remember, in the 1950s technology was still in its relative infancy; it was only in 1957 that the Soviets launched the first earth-orbiting satellite (Sputnik I.)

The Wahiawa facility was positioned to pick up all radio signals from Asia and the Pacific region, but the antenna was so sensitive that it could also pick up signals from around the world. Its sub-antennas in a complete circle also let operators inside know the direction from which the signal was coming.

Although human intelligence gathering efforts continued, technology played a greater role in the collection of information. The 1950s saw a greater capability of aerial reconnaissance in intercepting voice, radiotelephone, facsimile or Morse code communication, either transmitted in the clear or encrypted.

In addition, electronics were beginning to be able to pick up non-communications signals, such as the releases from foreign radar, and signals sent back from missiles or satellites that indicate performance and operation during a flight.

Supporting this aerial surveillance, during the 1950s and 1960s, work on ways of improving the capabilities and performance of high-frequency direction-finding equipment was improving – part of that research was the refinement of circular arrays, the CDAAs.

The worldwide network, known collectively as “Iron Horse”, could detect and locate Soviet submarines and other high frequency communications almost anywhere on the planet.

The system was wound down at the end of the Cold War; in the mid-1990s, the network of facilities were started to be torn down. On October 4, 1998, the Wahiawa facility ceased operations and was dismantled in 2005.

In September 2007, it was completely removed to make way for new buildings of the Hawaiʻi Regional Special Operations Center (HRSOC;) the military relocated its state-of-the-art intelligence and data gathering and analysis facility, related to security operations in the Pacific, out to the Kunia Tunnel.

The image shows AN/FRD-10 Circularly Disposed Antenna Array (CDAA) at NCTAMS (Facility 314,) the “Elephant Cage,” that used to be at Wahiawa. In addition, I have included other related images in a folder of like name in the Photos section on my Facebook and Google+ pages.

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